Emphasis on improved farming yields per acre as well as the reclamation of heretofore unsuitable land areas for housing, agriculture and silviculture has developed the drainage industry into a burgeoning field of enterprise. This growth has been encouraged by the development of lightweight, inexpensive polyvinylchloride (PVC) plastic pipe which has virtually replaced the heavier more expensive ceramic tile that was the mainstay of the industry twenty five years ago. In addition to its lower cost, PVC pipe's popularity also results from its adaptability to rapid, continuous installation since it is manufactured in continuous lengths up to 5,000 feet which do not require joining or sealing at repeated intervals. Thus, the cost savings associated with both such plastic continuous length pipes and its simplified and rapid installation have encouraged increased utilization of this means of improving crop yield or reclaiming otherwise unusable land areas. PVC drain pipe and drain pipe fabricated of other plastic materials now accounts for nearly all of the drain pipe installed in the United States.
Technological improvements in the equipment which trenches the soil and installs such plastic drain pipe have not been as great. Much conventional trenching equipment is available but it has generally been found to be unsuitable for drain pipe trenching applications. The most common type of trencher vaguely resembles a ferris wheel and comprises a plurality of fixed buckets transversely positioned between two rigid circular frames. The frames include gear drive teeth disposed about their outer peripheries which are engaged by a pair of drive sprockets which are powered by a prime mover. The sprockets disposed on the outer periphery of the rotating wheel tend to snag and collect roots and other debris. Therefore, it has been found necessary to secure outwardly extending side rooters to the circular frame. A trench which is dug with a bucket from ten to twelve inches in width must be at least three inches greater in width on each side due to the circular frame and another three inches wide on each side because of the side rooters. A bucket from ten to twelve inches wide may thus produce a trench nearly two feet in width. Digging a trench two feet wide to receive a six inch drain pipe is highly undesirable from both energy and ecology standpoints since not only is an unnecessary quantity of soil displaced but also such soil must be replaced.
The apparent solution of narrowing the width of the bucket itself is only illusory inasmuch as this dual frame design necessarily produces a trench approximately one foot wider than the bucket width. Hypothetically, the only way a trencher of this design could produce a trench one foot wide would be to construct it without buckets, circular frames or side rooters. It is apparent that such approaches are not feasible.
A trencher of conventional design incorporating buckets approximately three to four inches wide which would dig a trench approximately sixteen inches wide will encounter several difficulties. The major difficulty with such a narrow bucket is that of emptying it when digging in dense or wet soil, particularly clay. The dense soil tends to compact within the bucket and requires substantial additional scraping and cleaning components which will be vulnerable to damage by rocks within the buckets and which will substantially increase the energy requirements of the trenching wheel. In other words, the ease with which a conventional bucket may be emptied or the probability that such a conventional bucket will empty itself is in direct proportion to the size of the bucket. A bucket which fails to empty functions more as a wedge than a scoop--further increasing the horsepower requirements of the trencher while decreasing its digging and earthmoving capability.